Modern digital cameras can produce very high resolutions at very affordable prices. Four megapixel imagers are now commonplace and eight megapixel devices will soon be commercially available. With 4-8 megapixels possible in every frame of video, thirty frames per second in a standard format can tax even a broadband communications channel.
Not every part of a picture frame is of interest, and sometimes the user wants to zoom in on some particular part. Optical zooming can be used to zoom in on a subject in the center of the imagers field of view (FOV), and digital zoom can be used to enlarge any area in a region of interest. Digital zooming can be done very quickly because it is electronic, but optical zooming can take some time because the lens must be moved. Optics have an advantage in being able to capture detail, but the very dense pixel configurations now available in image devices is taking away a lot of that advantage.
Complex and bulky optics are sometimes not appropriate or practical in extreme applications. Such optics can also be too expensive, too vulnerable, too heavy, or too big. This is especially true in unmanned aerial vehicles (UAV's) that use cameras to fly and spot targets in hazardous areas and situations. Large complex optics are impractical for a number of reasons in UAV's, and the communication channels also have very limited bandwidths.